In the UML Activity diagram, actions may be organized into swimlanes. Swimlanes organize responsibility for activities by the organizational unit in which the activity takes place.
Definition of a swimlane: An organizational unit
Each swimlane represents an organizational unit. You may select any swimlane and add a definition to it by selecting Edit from the drop-down list box or simply double clicking on the swimlane.
Adding swimlanes
Swimlanes are turned on in a UML Activity diagram via a boolean selection property in the diagram definition.
1 Open Diagram Properties (select Edit, Diagram Properties, or right-click on an empty area of the diagram workspace and select Diagram Propertiesclick).
2 Select the Swim Lane property to be Vertical.
Result
Partitioning an Activity diagram into swimlanes is optional. Swimlanes, if used, are always vertical in a UML Activity diagram.
Drawing a swimlane
To draw a swimlane, select the Org. Unit tool from the toolbar (the icon shows two parallel lines), and place it on the diagram. It puts itself adjacent to an existing swimlane on the diagram.